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Subject[PATCH v3 2/3] mm: kmemleak: Simple memory allocation pool for kmemleak objects
Date
Add a memory pool for struct kmemleak_object in case the normal
kmem_cache_alloc() fails under the gfp constraints passed by the caller.
The mem_pool[] array size is currently fixed at 16000.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---
mm/kmemleak.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 52 insertions(+), 2 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 5ba7fad00fda..2fb86524d70b 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -180,11 +180,17 @@ struct kmemleak_object {
#define HEX_ASCII 1
/* max number of lines to be printed */
#define HEX_MAX_LINES 2
+/* memory pool size */
+#define MEM_POOL_SIZE 16000

/* the list of all allocated objects */
static LIST_HEAD(object_list);
/* the list of gray-colored objects (see color_gray comment below) */
static LIST_HEAD(gray_list);
+/* memory pool allocation */
+static struct kmemleak_object mem_pool[MEM_POOL_SIZE];
+static int mem_pool_free_count = ARRAY_SIZE(mem_pool);
+static LIST_HEAD(mem_pool_free_list);
/* search tree for object boundaries */
static struct rb_root object_tree_root = RB_ROOT;
/* rw_lock protecting the access to object_list and object_tree_root */
@@ -451,6 +457,50 @@ static int get_object(struct kmemleak_object *object)
return atomic_inc_not_zero(&object->use_count);
}

+/*
+ * Memory pool allocation and freeing. kmemleak_lock must not be held.
+ */
+static struct kmemleak_object *mem_pool_alloc(gfp_t gfp)
+{
+ unsigned long flags;
+ struct kmemleak_object *object;
+
+ /* try the slab allocator first */
+ object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp));
+ if (object)
+ return object;
+
+ /* slab allocation failed, try the memory pool */
+ write_lock_irqsave(&kmemleak_lock, flags);
+ object = list_first_entry_or_null(&mem_pool_free_list,
+ typeof(*object), object_list);
+ if (object)
+ list_del(&object->object_list);
+ else if (mem_pool_free_count)
+ object = &mem_pool[--mem_pool_free_count];
+ write_unlock_irqrestore(&kmemleak_lock, flags);
+
+ return object;
+}
+
+/*
+ * Return the object to either the slab allocator or the memory pool.
+ */
+static void mem_pool_free(struct kmemleak_object *object)
+{
+ unsigned long flags;
+
+ if (object < mem_pool || object >= mem_pool + ARRAY_SIZE(mem_pool)) {
+ kmem_cache_free(object_cache, object);
+ return;
+ }
+
+ /* add the object to the memory pool free list */
+ write_lock_irqsave(&kmemleak_lock, flags);
+ list_add(&object->object_list, &mem_pool_free_list);
+ write_unlock_irqrestore(&kmemleak_lock, flags);
+}
+
/*
* RCU callback to free a kmemleak_object.
*/
@@ -469,7 +519,7 @@ static void free_object_rcu(struct rcu_head *rcu)
hlist_del(&area->node);
kmem_cache_free(scan_area_cache, area);
}
- kmem_cache_free(object_cache, object);
+ mem_pool_free(object);
}

/*
@@ -552,7 +602,7 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
struct rb_node **link, *rb_parent;
unsigned long untagged_ptr;

- object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp));
+ object = mem_pool_alloc(gfp);
if (!object) {
pr_warn("Cannot allocate a kmemleak_object structure\n");
kmemleak_disable();
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